Missing crypto cost basis
What a missing cost basis means for crypto and gold
If your cost basis for crypto or gold is missing, you can't prove what you paid for assets you later sold or exchanged. Cost basis isn't just the ticket price, fees or commissions count, too. Without this, there's no accurate way to show your gain or loss, and the tax bill may end up higher than it should be.
This usually happens with older coins or metals, especially if they came from platforms that no longer exist, or wallets where the full transaction story's incomplete. Often, the fastest way to find evidence is with exchange exports. These are covered in crypto exchange tax reports. Try to start rebuilding your records now, since account data gets harder to retrieve after a few years.
Steps to rebuild purchase history
Start with anything you've saved: downloadable exchange trade files, bank records showing deposits you used to buy, and invoices from bullion dealers if you bought gold or silver. If you moved assets between your own wallets, check a blockchain explorer. These sites detail every transaction, with date and quantity, but don't include a currency price.
- Collect every exchange file or statement for each year you held assets.
- Match wallet transfers, flagging internal moves so you don't double-count.
- Record the local currency value of each purchase, along with where you got the rate.
Create a simple log for each asset: note the date, asset type, amount, price, fees and where each came from. It doesn't have to be flawless; just use the same method throughout. See the records you should keep for a more detailed list.
How tax authorities treat a missing cost basis
Every tax office sets its own rules. Some may accept your best documented estimate of what you paid, while others set the cost basis at zero if you can't back it up, making the sale value fully taxable. Expect to be asked for your records. Gaps or unclear items may get extra attention from an auditor.
If you cannot find all the details, keep your workings and state your methods in writing. Get help from a qualified adviser if you're unsure. It's not usually too late to correct past mistakes, see how to correct unreported crypto or foreign income for what to do next.
Frequently asked questions
What if I have no records at all for old crypto purchases?
You need to check what your tax authority requires. Some will accept a careful, well-documented estimate, but others default to zero cost, which means tax is due on the full proceeds. Start trying to piece things together from exchange files, old bank entries and transaction history on-chain. To cover yourself, note how you arrived at any values. Get confirmation from a tax professional or your revenue authority for your situation.
Can a blockchain explorer prove my cost basis?
No, not fully. A blockchain explorer shows dates and amounts, plus which addresses sent or received funds, so it helps you prove that you controlled specific coins at a given time. But it doesn't provide your actual purchase price in your own currency. You'll need to find or estimate those figures elsewhere. Crypto prices can change quickly, and results may be different than you expect. Ask a professional or your local tax authority exactly what documentation they require.